This invention relates to a process for producing carbon black and an apparatus therefor and, more specifically, to a process and an apparatus for producing a carbon black which has both a primary structure and tinting strength on high levels.
Of the properties inherent in carbon black, the primary structure and tinting strength are regarded as important attributes for greatly enhancing and reinforcing the properties of rubber into which the carbon black is compounded.
By "primary structure" is meant the nondestructive aggregate evaluated in terms of dibutyl phthalate absorption number of compressed sample defined in ASTM D3493-85a (the number being hereinafter called "24M4DBP" for brevity). Known manufacturing processes for carbon black with high 24M4DBP include the following. One process involves the introduction of feedstock oil as divided into principal and secondary feedstocks into a reaction zone where they are thermally decomposed by high-temperature combustion gas formed by burning fuel oil (U.S. Pat. No. 3,952,087). Another process consists in introducing high-temperature combustion gas into a reaction zone which is reduced in diameter downstream in throat-like fashion and inserting a feed-stock oil spray nozzle from the upstream side into the reaction zone along the axis of the zone, with the degree of nozzle insertion adjusted so as to change the point at which the feedstock oil is issued (Japanese patent application Kokai publication No. 52-85995). These processes permit some increases in 24M4DBP.
The conventional processes, however, have the disadvantage of broadening the aggregate distribution and accordingly bringing about a remarkable reduction in the tinting strength. To overcome this disadvantage, the present applicant has previously proposed a process whereby a plurality of separately produced streams of gas containing a carbon black precursor is led at a high speed into a principal reaction zone for impingement (Japanese patent publication No. 62-10581) and an improvement of the process 0 (Japanese patent publication No. 62-20227). These processes achieve further improvements in 24M4DBP over the conventional techniques such as the introduction of feedstock oil in divided streams. However, they involve difficulties in simultaneously attaining an enhancement of tinting strength.
Thus, primary structure and tinting strength are contradictory properties of carbon black. No technique has hitherto been developed which is effective in increasing both of the properties.